Genetic resources of tea in Japan: History and new direction in research

Since the Meiji period, Japan has actively collected and preserved domestic and foreign genetic resources of tea for breeding. The National Agriculture and Food Research Organization (NARO), Japan possesses one of the world's largest genetic resources of tea collected from 14 countries and regions. To efficiently utilize these genetic resources for various research purposes, including breeding, it is crucial that the characteristics of these genetic resources are accurately understood. Recently, analyses of genetic diversity using DNA markers have been actively conducted. Moreover, analysis of the diversity of NARO’s genetic resources of tea using Simple sequence repeat (SSR) markers revealed a large extent of genetic differentiation between germplasms of domestic and overseas origin. The genetic diversity of the domestic accessions, as opposed to the foreign accessions, was limited. Therefore, to expand the genetic diversity of breeding materials, the utilization of genetic resources introduced from overseas is vital. Core collections of NARO’s genetic resources of tea were selected using the SSR marker genotype data. These core collections are very useful to exploit the abundant diversity of tea plants. Moreover, combining core collections and genome analyzing technology would enable the creation of new breeding materials and the identification of useful loci of important agricultural traits.